Exposure to metals during development and early in life is a critical public health issue, and both water and food can be vectors of exposure, especially to inorganic arsenic. However, limited data are available on the dietary exposure to metals for U.S. infants or the subsequent expression of this exposure in established biomarkers. Recent data, including our own preliminary results, suggest that rice and rice products are significant contributors to inorganic arsenic exposure. Building on the Dartmouth Superfund Program's prospective pregnancy cohort, this pilot project will explore dietary sources of metal exposure in a cohort of infants through the first year of life. The goal is to identify the contribution of diet to both metal exposure and the ability to reduce metal toxicity via potential modifying factors such as folate, iron, and vitamin B. The project will focus particularly on exposure through breast milk and infant formulas, but will also collect data on the period when infants transition to solid foods, especially rice cereals. Information regarding the diet of the infant (including breastfeeding; amounts of formula, cereals, solids, and water being consumed; and vitamin supplementation) will be collected every 2-3 months during the first year of life via a phone questionnaire. Toenail clippings and a urine sample will be taken from the infant at ~4 months, and lactating women who are using a breast pump to store milk for their infants will be encouraged to provide a sample of their milk at the same time. We will also obtain toenail clippings from the infant and mother at ~12 months, together with information about maternal diet over the past year using a food frequency questionnaire. We will compare the infant dietary data with arsenic in the toenail and urine samples, and also use data on arsenic metabolites in the urine sample as a marker of infant ability to metabolize arsenic postpartum. If we are able to identify the sources of infant metal exposure, or factors that appear to mitigate the effects of this exposure, we can initiate intervention studies to identify specific dietary recommendations for prevention of adverse outcomes.